In recent years, a cutting technology has been widely applied in a process of fragmenting substrates such as a wafer, touchscreen glass, and a liquid crystal display. However, in a cutting process, these to-be-cut substrates are very likely to generate a crack after suffering cutting stress due to poor toughness and high brittleness. Consequently, problems such as poor reliability and a failure arise on a cut substrate fragment (also referred to as a cut unit).
In the prior art, a crack detection line extending along one direction is disposed on one detection surface of a cut unit, and whether a crack intersecting the crack detection line exists on the cut unit is determined by detecting a breaking status of the crack detection line. However, a direction of a cutting crack is uncertain. In other words, a crack in any direction may be generated in a cutting process. A crack detection line extending along only one direction exists on one detection surface of the cut unit. In this case, only a cutting crack intersecting the foregoing unidirectional extending crack detection line can be detected. If there is a cutting crack that does not intersect the crack detection line, the cutting crack cannot be detected in the prior art, causing low crack detection precision for the cut unit.
How to detect a crack on the cut unit more precisely is continuously researched in the industry.